Tag Archives: beepboops

DASYRAC is my voltage-controlledEurorack modularsynthesiser. It’s a synthesiser because it creates positive and negative voltages which turn into vaguely musical positive and negative sound waves when they’re sent through a speaker coil. It’s modular because it’s built up from modules and instruments which each have a specific role to perform in the process of synthesis. It’s Eurorack because the modules use Doepfer’s Eurorack specfications for size (3U) and voltage (+/- 12V & +5V supply rails, plus gate and pitch CV buses which only Doepfer’s modules seem to use).

Finally, it’s voltage-controlled because the modules are connected by patch cable and signal one another using voltages. Signal types include:

triggers – a very short pip of steady positive voltage used trigger a modulation source or function generator, reset a sequence, etc

clocks – a series of short triggers used for timing, usually evenly spaced

gates – a sustained steady positive voltage which is held “high” for the length of a note or other event

modulation – a non-steady voltage which is used to control module functions

pitch – a voltage which is used to represent the pitch of a note, where one volt corresponds to one octave (1v/oc); usually steady, but not always

audio – a varying voltage which rapidly swings positive and negative and is intended to be heard at some point

Because they’re all made of the same stuff (flowing electrons), these signals can play one another’s roles – audio and gate signals can both be a modulation source, sufficiently fast clocks can be an audio source, audio can also be a clock source, pitch can be a modulation source, modulation can be a pitch source, and triggers can even be an audio source as long as you’re into snaps and clicks. Part of the fun of modular synthesisers is just seeing what happens when you connect modules together in unconventional ways.

Here’s a recent photo of a cable-free DASYRAC with colour-coding to show what the different modules do. If a module has more than one function, it gets more than one colour.

A rainbow of possibilities!

The multicoloured thing at the bottom left is a Make Noise 0-Coast synthesiser – it’s not a Eurorack module itself, but it can patch into and out of DASYRAC just fine. As you can see, it’s like a tiny self-contained modular system in and of itself. There’s also an ARP Odyssey floating around somewhere.

Everything starts with a supply of tasty electrons from two power supplies (in red). All the active modules connect to the two power supplies at the back by ribbon cable.

Middle row: 4ms Row Power 30

Bottom row: Tiptop uZeus

Maybe I’m being too specific about what makes noises…

The green modules are audio sources. They speficially create oscillating voltages which are intended to be heard aloud at some point. Some are more fully featured than others – the green module in the centre top row is an entire self-contained instrument – it’s a recreation of the clap sound from a Roland TR-909. Audio sources which produce a musical tone – oscillators – have a 1V/Oct socket which takes a pitch voltage. The green module at the top left is a sound playback instrument.

Not shown: Korg ARP Odyssey (fixed-architecture synthesiser which can be run as a plain CV-controlled dual oscillator if need be)

The blue modules are “non-audio” voltage sources and include function generators like the Rampage, step sequencers like the SQ-1, procedural sequencers and clock sources like Tuesday, and random voltage generators like Turing Machine. Their job is to provide discrete or continuous voltages which can drive melodies, rhythms, filters, or whatever else accepts voltage control. If they’re running fast enough, voltage sources can also be used as oscillators in their own right.

The yellow modules are the effects and filters. Filters in particular make the incoming sound quieter at particular frequencies and also colour the sound in characteristic and desirable ways. They are “voltage controlled filters” (VCFs) because they take an input voltage to control their cutoff frequency, which is the frequency where the filters take effect. There’s also some effects modules for even more retro colour. Many of these modules can be made to create noises of their own without any input, which also makes them audio sources in their own right!

Violet modules are a special thing called VCAs – voltage controlled amplifiers/attenuators. A VCA takes two signals – an input and a modulating signal – and outputs a quieter/louder version of the input signal with amplitude/volume tracking the modulating signal. VCAs are where a long steady beeeeep sound is contoured into a short pip or a long mournful wail. Even better: a quadrature VCA can invert the incoming signal – chuck a sine wave into it as a modulator and you’ve got Dalek voices.

Overall, DASYRAC is an eclectic system with features from the mainstream East Coast school (character filters, rich saw/pulse oscillators), the artier West Coast school (waveshapers, function generators, sequencers, low pass gates), old timey classics (spring reverb, shift register noise) and fun new possibilities (digital audio playback).